An application , It all boils down to a pile of code , Is static , The process is the program that is being executed , When a program is running , It is possible that multiple processes are executing concurrently . Process versus thread comparisons
Process is the basic unit of system resource allocation .
A process can contain multiple threads , Belong to one to many , All resources of the process , Shared by threads within it .
Threads are the smallest unit , If a process completes a function , So thread is the basic unit of this function .
Resources between processes are not shared , Multi process consumption is high , Difficulty ; All threads in the same process enjoy resource sharing , Low multi threading consumption , Difficulty is small .
Similarities between processes and threads ： To improve the efficiency of the program , Have the priority of implementation .
Multi process ：
from multiprocessing import Process
def foo(name):
print('hello ,%s'%name)
if __name__ == '__main__':
p1 = Process(target=foo,args=('world!',))
p2 = Process(target=foo,args=('Python!',))
p1.start()
p2.start()
print(' The main process ')
The main process and child processes execute concurrently Be careful ： Process The object can only be in if name == ‘main’: Create , Otherwise, it will report a mistake .
Process Built in method of ：
p.start
Start the process , And call... In the child process p.run()
p.run() How to run a process when it starts , It is it that calls target function , Our custom class must implement this method p.terminate() Force end process p, No cleaning operations will be carried out , If p Create child process , This sub process becomes a zombie process . If p If a lock is retained, it will not be released , Which leads to deadlock p.is_alive If it is still running , Then return to Truep.join([timeout]) Main thread waiting p suspend ,timeout Optional timeout for
Process attribute ：
p.daemon
The default is False, If it is set to True, representative p Daemons running in the background , When p When the parent process of is terminated ,p Also terminate ,p You can't create your own new process yet , Must be in p.start() Set before
p.name The name of the process p.pid Process pidp.exitcode The process at run time is None, If -N, To signal N end
One has at least one dream , There's a reason to be strong . If the heart has no place to rest , I'm wandering everywhere .
